Faculty Profiles - SAITO, Nagahiro

Papers - SAITO, Nagahiro

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Solution plasma synthesis of nitrogen-doped carbon dots from glucosamines: Comparative fluorescence modulation for dopamine detection International coauthorship International journal

Treepet S., Duangmanee T., Chokradjaroen C., Kim K., Saito N., Watthanaphanit A.

Carbon Vol. 231 2025.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Carbon

The intriguing fluorescence characteristics of carbon dots (CDs) have led to many sensor applications, particularly for dopamine (DA), a molecule linked to various diseases. This study prepares CDs from glucose and glucosamine (nitrogen-free and nitrogen-containing precursors) using a simple solution plasma process (SPP). We explore how nitrogen elements and counterions in glucosamine (hydrochloride and sulfate) affect CD properties and their ability to modulate fluorescence for DA detection. Glucosamine offers three advantages over glucose: (i) single-step CD synthesis via SPP, (ii) enhanced fluorescence of CDs, and (iii) improved fluorescence response to DA. We investigate the DA detection capabilities of N,S-CDs (from glucosamine sulfate) and N,Cl-CDs (from glucosamine hydrochloride). Both can sense DA with distinct photoluminescence responses. N,S-CDs show selectivity and fluorescence brightening upon DA interaction, with a detection limit of 33.05 μM. N,Cl-CDs demonstrate higher sensitivity with a lower detection limit of 0.1212 μM through fluorescence quenching. Silver ions (Ag+) may also contribute to N,Cl-CDs quenching; however, the observed color change to gray due to silver nanoparticle (AgNP) formation helps pinpoint the quenching substance. The varied photoluminescence responses arise from different surface functional groups: N,S-CDs have amino-rich surfaces, while N,Cl-CDs have conjugated carbonyl-rich surfaces. This study illustrates the mechanisms of DA detection and AgNP formation, suggesting the potential of CDs in medical diagnostics as selective tools for disease diagnosis. Additionally, we compare the DA sensing methodology of our CDs with existing literature, highlighting the advantages of our sensor.

DOI： 10.1016/j.carbon.2024.119705

A Bandgap-Tuned Tetragonal Perovskite as Zero-Strain Anode for Potassium-Ion Batteries International coauthorship International journal

Yang W., Huang J., Zheng Q., Chen L., Orita A., Saito N., Zhang Z., Zhang Y., Yang L.

Angewandte Chemie - International Edition Vol. 63 ( 52 ) 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Angewandte Chemie - International Edition

PIBs are emerging as a promising energy storage system due to high abundance of potassium resources and theoretical energy density, however, progress of PIBs is severely hindered by structural instability and poor cycling of anode material during continual insertion and extraction of larger-sized K+. Hence, developing anode material with structural stability and stable cycling remains a great challenge. Herein, band gap-tuned Mo-doped and carbon-coated lead titanate (CMPTO) with zero-strain K+ storage is presented as ultra-stable PIBs anode. Mo doping introduces narrowed band gap and optimized crystal lattice for enhanced intrinsic electron and ion transfer. Demonstrated by in situ XRD characterizations, the crystal structure stays stable with unchanged peak positions, fully revealing zero-strain characteristic of CMPTO anode during potassium storage for stable cyclic capability. Ultimately, CMPTO anode achieved ultra-stable cycling performance of 7000 cycles at 500 mA g−1 with high capacity retention of 90 % and considerable specific capacity of 130.9 mAh g−1 after 600 cycles at 100 mA g−1; with relatively large density, CMPTO realized eminent volumetric capacity of 1111.09 mAh cm−3 and ultra-long cycling life of 10000 cycles at 7041 mA cm−3. This work introduces a promisingly new route into developing anode materials with ultra-stable performance for PIBs.

DOI： 10.1002/anie.202412706

Interphase Optimum via Synergistic Effect of Poly(1,3-dioxolane) Electrolytes and Lithium Difluorophosphate for Stable Lithium Metal Batteries International coauthorship International journal

Hu A., Liao Z., Yang Q., Huang J., Wei Z., Sun Y., Zhao E., Zhang Z., Yang L., Saito N., Orita A.

Advanced Functional Materials Vol. 34 ( 51 ) 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Advanced Functional Materials

Solid polymer electrolytes (SPEs) hold great promise for future applications of high-energy lithium metal batteries (LMBs). Unfortunately, inadequate room-temperature ionic conductivity, sluggish interfacial charge transport, and uncontrolled electrode/electrolyte interface reactions severely limit their widespread applications. Herein, poly(1,3-dioxolane) electrolytes (PDEs) are prepared in situ by introducing lithium difluorophosphate (LiDFP, LiPO2F2) as a multifunctional additive, which not only achieves excellent ionic conductivity but facilitates interfacial charge transport. Meanwhile, a high-mechanical-stability organic–inorganic hybrid solid electrolyte interphase (SEI) is formed by the synergistic effect of PDEs and LiDFP. The enrichment of LiF and LixPOyFz species in SEI formed by the preferential reduction of LiDFP ensures outstanding mechanical stability, and the ring-opening polymerization of 1,3-dioxolane provides the SEI excellent adaptability to the repetitive volume changes of lithium metal anode, which mitigates crack and regeneration of SEI and reduces side reactions between active Li and electrolytes. Therefore, based on PDEs, the symmetric Li cell enables steady cycling for 2000 h. The Li-LiFePO4 cell achieves superior long-term cycling stability (over 1200 cycles) and wide operating temperature (−20 ∼ 60 °C). Also, the Li-LiNi0.6Mn0.2Co0.2O2 exhibits favorable cycling stability. This study provides solutions to ongoing pain point issues of SPEs and facilitates practical applications of SPEs in high-energy LMBs.

DOI： 10.1002/adfm.202410282

Few-Layer MoS<inf>2</inf> on a SiO<inf>2</inf>/Si Wafer through Sulfurization Chemical Vapor Deposition with a Vaporization-Shadowing Effect International journal

Zhu Z., Liu Y., Sato K., Niu J., Chokradjaroen C., Sawada Y., Saito N.

ACS Applied Nano Materials Vol. 7 ( 17 ) page： 20257 - 20266 2024.9

Language：English Publishing type：Research paper (scientific journal) Publisher：ACS Applied Nano Materials

This study aimed to synthesize few-layer MoS2 on SiO2/Si using sulfurization chemical vapor deposition toward beyond-5G and 6G communication. Fabric-like MoO3(s) was directly placed onto a SiO2/Si substrate to lower the oxygen potential, which is achieved through a shadowing effect on vaporization. Successful results were achieved, yielding MoS2 thin films with a coverage of more than 74% and a crystal size in the range of 50 to 600 μm. Two distinct pathways for MoS2(s) formation from MoO3(s) via MoO2(s) and MoS3(s) were also uncovered. The shadowing effect of MoO3(s) vaporization facilitated the two-dimensional growth of MoS2 by mitigating oxygen partial pressure. Therefore, sulfurization chemical vapor deposition shows great application potential in synthesizing high-quality MoS2 thin films with substantial crystal size and coverage, making them suitable for next-generation communication devices.

DOI： 10.1021/acsanm.4c03188

Solid-state rigid polymer composite electrolytes with in-situ formed nano-crystalline lithium ion pathways for lithium-metal batteries International coauthorship International journal

Wei Z., Huang J., Liao Z., Hu A., Zhang Z., Orita A., Saito N., Yang L.

Energy Storage Materials Vol. 72 2024.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Energy Storage Materials

Polymer-based solid-state electrolytes with excellent processability and flexibility are ideal candidates for commercialisation in lithium-metal batteries. However, the current polymer-based solid-state electrolytes still have many problems such as low ionic conductivity, limited Li+ transport number and high interfacial resistance with electrodes. To address the above challenges, a solid-state rigid polymer composite electrolyte with high ionic conductivity (2.8 mS cm−1) has been prepared based on the rigid polymer poly(2, 2′-disulfonyl-4, 4′-benzidine terephthalamide) (PBDT). Locally aligned PBDT-EMImN(CN)2 grains are interspersed with in-situ formed interconnected LiFSI to form the structure of the polymer composite electrolyte. The formation of defective LiFSI nanocrystals at grain boundaries inside the polymer electrolyte acts as additional conductive networks providing fast Li+ transportation (tLi+ = 0.59). The flexible region in the electrolyte gives excellent interfacial impedance (32.5 Ω cm2) with Li-metal electrode. The Li||Li batteries can be stably cycled for over 1000 cycles at 1 mA cm−2 (25 °C). The assembled Li||LiFePO4 batteries exhibit excellent cycling and multiplication performance over a wide operating temperature (from −20 to 60 °C). Moreover, this electrolyte material exhibits compatibility with high-voltage cathode LiNi0.6Mn0.2Co0.2O2 batteries. This electrolyte and design strategy is expected to inspire the realization of all-weather practical solid-state lithium-metal batteries.

DOI： 10.1016/j.ensm.2024.103714

Improving the durability and anti-poisoning properties of platinum catalysts by carbon shell encapsulation: A promising approach for both cathode and anode catalysts for polymer electrolyte membrane fuel cells

Park J.H., Saito N., Kawasumi M.

International Journal of Hydrogen Energy Vol. 72 page： 642 - 651 2024.6

Language：English Publishing type：Research paper (scientific journal) Publisher：International Journal of Hydrogen Energy

Carbon shell encapsulation has emerged as an effective strategy for enhancing the durability of Pt-based electrocatalysts for polymer electrolyte membrane fuel cells (PEFCs). Here, a nitrogen-doped carbon shell-encapsulated Pt catalyst supported on Ketjen black (Pt@C/KB) was synthesized, and its catalytic performance was characterized. The oxygen reduction reaction (ORR) performance and anti-poisoning properties were investigated in 0.1 M HClO4 with and without H2SO4 or H3PO4 poisoning, using a rotating ring-disk electrode (RRDE) technique. Despite a decrease in the electrochemical surface area (ECSA), Pt@C/KB encapsulated by a thin graphene-like carbon shell (<1 nm thick) showed high selectivity for the four-electron reaction due to its superior anti-poisoning properties, as well as improved ORR activity and durability. The H2O2 yield of Pt@C/KB, the precursor of hydroxyl radicals, was decreased approximately one third compared to bare Pt catalyst and the gap was more pronounced in the low potential (E ≤ 0.1 V/RHE) where close to practical anode potential, suggesting that Pt@C/KB can be applied as a new anode catalyst. Applying carbon core-shell catalysts to both the cathode and anode is a prospectively effective approach for improving the cell performance by improving the ORR activity and anti-poisoning properties, as well as for extending the lifespan of PEFCs.

DOI： 10.1016/j.ijhydene.2024.05.394

Accelerated Capacity and Cycling Performance via Facile Instantaneous Precipitation Induced Amorphization for Lithium-Ion Batteries Reviewed International coauthorship

Yang W., Huang J., Zhang Y., Saito N., Zhang Z., Yang L.

Small Methods Vol. 7 ( 11 ) 2023.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Small Methods

Conversion-alloying anodes have garnered escalating attention with high theoretical capacity, however, they are seriously hindered by large volume distortion and capacity fading. To counter, structural modification needs more exploration. Herein, advantageous structure and high-performance are realized in new amorphous PbSb2O6 (PSO-a) nanosphere via facile instantaneous precipitation induced amorphization; conversion-alloying mechanism endows it with prominent lithium-storage capability; nanostructure can shorten ion-transfer distance and accommodate volume change outside the bulk of PSO-a; and loosely-stacked isotropic amorphous structure can enhance kinetics both at electrode/electrolyte interfaces and in the bulk. Volume change is synergistically stabilized from within to outside the bulk, leading to accelerated capacity and cycling. As expected, when employed in half-cells with 1 m LiPF6 in ethylene carbonate/diethyl carbonate/dimethyl carbonate/fluoroethylene carbonate (3:3:3:1 by mass) as electrolyte, glass microfiber filter as separator, and pure lithium foil as counter electrode, it realizes eminent performance with high specific capacity of 1512.6 mA h g−1 at 0.1 A g−1 and 755.1 mA h g−1 after 1000 cycles at 3 A g−1. To the best of the authors' knowledge, this is the first time PbSb2O6 is utilized as high-performance anode for lithium-ion batteries. Furthermore, this facile strategy provides a promising direction for high-performance amorphous anode material.

DOI： 10.1002/smtd.202300691

Correlation function of specific capacity and electrical conductivity on carbon materials by multivariate analysis Reviewed

Moon J., Yun H., Ukai J., Chokradjaroen C., Thiangtham S., Hashimoto T., Kim K., Sawada Y., Saito N.

Carbon Vol. 215 2023.11

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Carbon

An attention to a Li ion battery for electric vehicles has been attracted, but there are two huge problems: a short mileage and slow charging speed. Therefore, it is required to improve the specific capacity and electrical conductivity of the carbon material used for an anode and a conductive agent. To solve these problems, this study organized correlation analysis with descriptor vectors by collecting experimental properties including capacity and conductivity from 21 various types of carbon materials. Focusing on the flux of Li ion, it was found that the capacity was dependent on the intercalation of Li ions, which lead to propose the correlation equation based on the Hill equation. Furthermore, the intercalation occurred at the edge of basal plane lead an increase of the width of the gap between two graphene layers, followed by a diffusion through the basal plane, finally the expanded gap recovered its original width. Also, it was found that the variables which are sensitive to the conductivity are largely dependent on the defects and especially the number of graphene layers around the surface, which proposed a correlation equation that can predict the capacity and conductivity. To validate these functions, we checked the effectiveness of it with both experimental data from 27 previous studies and statistical method. As a result, it was confirmed enough to predict them. Finally, a candidate structure for improving the battery performance was proposed, thus our study aims to guide the exploration of electrode materials for LIBs.

DOI： 10.1016/j.carbon.2023.118479

Search for stable host materials as low-voltage anodes for lithium-ion batteries: A mini-review Reviewed International coauthorship

Zhang Y., Huang J., Saito N., Zhang Z., Yang L., Hirano S.i.

Energy Storage Materials Vol. 55 page： 364 - 387 2023.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Energy Storage Materials

The explosive demand for lithium-ion batteries (LIBs) in electric vehicles, portable electronics, and smart grids has spurred extensive research in recent years. The key to essential advances in LIBs depends on the search for stable host electrode materials with desirable energy and power densities. In the development of emerging stable host anode materials, the operating potential is an overlooked but crucial parameter because it deeply influences the energy, power, and safety of batteries. The ideal potential should not be too close to the lithium deposition potential like graphite (0.1 V vs. Li+/Li) which would trigger the formation of lithium dendrites under high rates, nor should be too high like spinel Li4Ti5O12 (> 1.5 V vs. Li+/Li) which compromises the batteries’ power and energy density. This mini-review firstly gives an account of several types of titanium-based and vanadium-based compounds as stable host anodes with the average operating potentials around or below 1 V vs. Li+/Li. The mechanisms for stable lithium storage and the origins of the low operating potentials are discussed by combining various characterization technologies. The key barriers and corresponding approaches are summarized for progressive electrochemical performance. Furthermore, several concise perspectives and challenges aiming at further theoretical prediction and practical application are provided.

DOI： 10.1016/j.ensm.2022.11.030

Nanoscale advanced carbons as an anode for lithium-ion battery Reviewed International coauthorship

Naraprawatphong R., Chokradjaroen C., Thiangtham S., Yang L., Saito N.

Materials Today Advances Vol. 16 2022.12

Authorship：Last author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Materials Today Advances

Nanoscale advanced carbons, including carbon nanotube, graphene, carbon nanosphere, porous carbon, and their derivatives, are represented as distinct types of material generate in various forms, structure dimensions, and properties. They feature a large specific surface area, excellent conductivity, high mechanical properties, tunable chemical functionality, and a broad potential window, which essentially require for lithium-ion battery systems. The nanoscale advanced carbons have been intensively researched and developed as a negative electrode component to improve battery performance. This review deliberately discusses structures, main properties, and synthesis methods that are directly related to the physical properties and chemical behaviors of the nanoscale advanced carbons. Moreover, currently good candidates for anode material for lithium-ion batteries were summarized. The importance of the primary function and the synergistic effect of nanoscale advanced carbons with active electrode species is emphasized. The systematic information from this review provides a promising tool that represents an essential reference for selecting anode electrode materials and designing the next generation of advanced lithium-ion batteries.

DOI： 10.1016/j.mtadv.2022.100290

Saccharide-originated fluorescent carbon dots synthesized by in-liquid plasma with controlled orderliness of carbon core through precursor alteration for selective and rapid metal ion detection Reviewed International coauthorship

Treepet S., Chokradjaroen C., Kim K., Saito N., Watthanaphanit A.

Materials Today Chemistry Vol. 26 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Materials Today Chemistry

Carbon dots (CDs) have grown interested in replacing metal-based quantum dots due to their fluorescent properties with low toxicity. The green synthesis, therefore, represents a contribution to this research field. Here, we demonstrate the synthesis of CDs from simple saccharides, including fructose, glucose, and sucrose, using an eco-friendly method—solution plasma (SP)—by applying plasma in the aqueous solution of the precursor. Variations and characterizations are conducted to understand the role or influence of each synthesis parameter, i.e. saccharide precursor's molecular structure, solution pH (2, 5, and 8), and post-treatment method (freeze-drying and heat-drying), in the materials' structure and fluorescent properties. Blue light-emitting CDs are prepared from all precursors of pH 5 and 8 through SP, followed by heat-drying. Results show that SP is responsible for the carbon core formation, and thus the precursor type affects the carbon core's orderliness. Heat-drying causes oxidation on the CDs' surface, whereby OH functional groups change to C=O. Among all samples, the CDs synthesized from fructose at pH 5 (Fru-CDs-5) perform the best photoluminescence property, having the highest quantum yield (QY) of 9.16% and exhibiting an outstanding ability to detect Fe3+ ions. This is the first attempt to evince the potential use of SP to synthesize CDs from natural carbon sources and obtain CDs exhibiting superior fluorescence properties without any doping and complex synthesis steps. In addition to offering a new synthetic approach, this work specifies the role of the SP and the effect of the saccharide's molecular structure, which is the most relevant synthesis parameters mandatory to obtain tailored CDs with precise control.

DOI： 10.1016/j.mtchem.2022.101139

Graphitic N-doped graphene via solution plasma with a single dielectric barrier Reviewed

Niu J., Chokradjaroen C., Saito N.

Carbon Vol. 199 page： 347 - 356 2022.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Carbon

Graphitic nitrogen-doped graphene (g-NG) with significantly high nitrogen content, i.e., 18.79 at.%, could be produced by the electrical discharge in liquid, so-called “solution plasma”, with a single dielectric barrier. The proposed system could reduce the excessive current, resulting in stabilizing the glow plasma and maintaining the overall temperature. It could promote the preservation of nitrogen atoms from evaporation during the synthesis process and the formation of a graphitic carbon framework. Moreover, the influence of the precursors, i.e., six-membered ring organic molecules with and without the substitution of nitrogen atoms and the nitrogen-based functional groups, was also investigated to provide the guideline for the synthesis of g-NG via this proposed method. The substitution of nitrogen atoms in the benzene ring could be used to synthesize g-NG with higher nitrogen dopants, compared to the benzene ring with only nitrogen-based functional groups.

DOI： 10.1016/j.carbon.2022.08.032

Two-Dimensional Crystal Growth of MoS<inf>2</inf> Thin Films from Sodium Dodecyl Sulfate Micellar Solutions and Wettability Between Solution and Substrate Open Access

Zhu Z., Liu Y., Sawada Y., Saito N.

Coatings Vol. 15 ( 1 ) 2025.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Coatings

In this study, the growth of 2D MoS2 thin films on SiO2/Si substrates was investigated using sodium dodecyl sulfate (SDS) micellar solutions, and the effects of SDS concentration and substrate treatment on crystal growth were evaluated. By increasing the SDS concentration, the wettability was improved, and uniform MoS2 crystal growth was promoted by micellar formation. When the SDS concentration exceeded 10−4 mol/L, the static contact angle sharply decreased, indicating uniform 2D material growth. The optimal conditions that enabled a uniform supply of Mo-based precursors were as follows: SDS concentration of 3.5 × 10−4 mol/L; Na2MoO4·2H2O concentration of 1.7 × 10−2 mol/L. The results indicate that solution-based processes using SDS are effective for 2D material growth, and they may be a valuable technique in future thin film device fabrication processes.

DOI： 10.3390/coatings15010004

Corrigendum to “Solid-state rigid polymer composite electrolytes with in-situ formed nano-crystalline lithium ion pathways for lithium-metal batteries” [Energy Storage Materials Volume 72 (2024) 103714] (Energy Storage Materials (2024) 72, (S2405829724005403), (10.1016/j.ensm.2024.103714)) Open Access

Wei Z., Huang J., Liao Z., Hu A., Zhang Z., Orita A., Saito N., Yang L.

Energy Storage Materials 2025

Language：English Publishing type：Research paper (scientific journal) Publisher：Energy Storage Materials

The authors regret. In the second paragraph in the introduction, we delete "The PBDT not only breaks the trade-off between ionic conductivity and modulus, but also provides a controlled macroscopic arrangement in the formed ionic gels." and here add "Wang et al [1] significantly enhanced the lithium ion conductivity by introducing a grain boundary network filled with LiFSI and LiBF4 nanocrystals into PBDT-gels. This polymer composite electrolyte exhibits not only good ionic conductivity but also high lithium ion transference number and mechanical modulus. Based on the excellent performance of such polymer electrolytes, a similar concept was designed and constructed in the PBDT matrix in our work, aiming to apply it in lithium metal secondary batteries." The authors would like to apologise for any inconvenience caused.

DOI： 10.1016/j.ensm.2025.104102

Enhanced energy storage efficiency of an innovative three-dimensional nickel cobalt metal organic framework nanocubes with molybdenum disulphide electrode material as a battery-like supercapacitor International coauthorship International journal

Palanisamy R., Pavadai N., Pavadai R., Saito N., Pattananuwat P., Sujaridworakun P.

Journal of Alloys and Compounds Vol. 1009 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Alloys and Compounds

Recently, metal-organic frameworks (MOFs) with transition metal sulfides have gained much attention as electrode materials for supercapacitors (SCs). In this work, 3D-NCMOF@MS NCs, incorporating two-dimensional molybdenum disulphide (2D-MS) nanosheets and three-dimensional nickel cobalt-MOF nanocubes (3D-NCMOF NCs) are synthesized by a solvothermal and precipitation process. Owing to their enhanced electrical conductivity and huge surface area, the 3D-NCMOF@MS NCs produce superior electrochemical responses in SCs compared to 2D-MS and 3D-NCMOF NCs. The results demonstrate that the synergistic 3D-NCMOF@MS NCs increased specific capacitance up to 1048 Fg−1 at 1 Ag−1, revealing outstanding cycle stability with a capacitance retention of 99.06 %. Besides, the exposed high-power density of 3D-NCMOF@MS NCs reached 400 W kg−1 as well as an outstanding maximum energy density of 188.64 Wh kg−1. Such synergistic effects of the multivalent states of Ni, Co, and Mo promote electrochemical characteristics, implying that the 3D-NCMOF@MS NCs could potentially be used in energy storage systems, boosting electrochemical performance.

DOI： 10.1016/j.jallcom.2024.176991

Platinum nanoparticles wrapped in carbon-dot-films as oxygen reduction reaction catalysts prepared by solution plasma sputtering International journal Open Access

Liu Y., Zhu Z., Wang P., Deng Z., Niu J., Sawada Y., Saito N.

Nanoscale Advances Vol. 7 ( 4 ) page： 1048 - 1060 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Nanoscale Advances

Fuel cells have become increasingly important in recent years because of their high energy efficiency and low environmental impact. However, key challenges remain in the widespread adoption of fuel-cell vehicles, including reducing Pt usage in catalysts and improving their durability. In this study, a high-performance Pt@carbon-dot-film core–shell catalyst was successfully synthesized using a nonequilibrium reaction field, i.e., solution plasma (SP) process, by adjusting the electrolyte pH. Four pH solutions (pH = 4.4, 7, 8, and 11) were employed as the discharge liquid environment for the SP process. The catalyst synthesized in the pH = 8 solution exhibited a mass activity of approximately 500 mA mg−1, which was twice as high as that of the commercial Pt/C catalyst (256 mA mg−1) with the same loading amount. The onset and half-wave potentials were 0.99 and 0.89 V, respectively, both of which exceeded those of commercial Pt/C catalysts (0.95 and 0.86 V, respectively). Furthermore, the enhanced catalytic performance corresponded to the Pt/C bonding between Pt and the carbon shell generated during the SP process.

DOI： 10.1039/d4na00818a

Surface functionalization of cellulose derived from hemp by tetraethyl orthosilicate (TEOS) and poly vinylidene fluoride (PVDF)-based composite separator membrane for lithium-ion batteries (LIBs) International coauthorship International journal Open Access

Sirichaibhinyo T., Thiangtham S., Saito N., Ummartyotin S.

Results in Engineering Vol. 23 2024.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Results in Engineering

Separators play a crucial role in enhancing the electrochemical performance of lithium-ion batteries (LIBs). However, achieving separators with exceptional electrochemical performance and high stability remains a significant challenge. In this study, we meticulously designed composite membranes based on polyvinylidene fluoride (PVDF) with varying contents of microcrystalline cellulose/tetraethyl orthosilicate (MCC/TEOS). The increase in hydrophilicity of PVDF by adding MCC-TEOS weight contents endowed the 3 wt% MCC/TEOS-based PVDF separator membrane with superior electrolyte absorption and reduced resistance, resulting in an impressive ionic conductivity of 0.514 mS/cm higher than the pristine PVDF membrane (0.253 mS/cm). Furthermore, the LIB cell utilizing the 3 wt % MCC/TEOS-based PVDF separator membrane consistently demonstrated stable charge/discharge profiles at a rate of 0.2C, achieving a specific capacity of 98 mAh/g, compared to only 43 mAh/g for the pristine PVDF membrane. These findings underscore the significant potential of MCC/TEOS as a biofiller for bio-membranes, making it an optimal choice for applications in LIBs.

DOI： 10.1016/j.rineng.2024.102807

Nitrogen-Doped Carbon Nanothin Film as a Buffer Layer between Anodic Graphite and Solid Electrolyte Interphase for Lithium-Ion Batteries International coauthorship International journal Open Access

Ukai J., Kim K., Matsuhara S., Yang L., Saito N.

ACS Omega Vol. 9 ( 23 ) page： 24372 - 24378 2024.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ACS Omega

Lithium-ion batteries are essential batteries for electric vehicle drive systems. Such batteries must provide stable performance over a long period of time. Therefore, the degradation or aging of the battery capacity must be improved. In the case of the current graphite anodes, graphite coated with an amorphous layer is used. It is known that the amorphous layer can reduce the irreversible capacity loss caused by the solid electrolyte interphase (SEI) layer. The amorphous carbon layers reduce the initial capacity due to higher electrical resistance. In this study, we aim to develop a buffer layer using nitrogen-containing graphene that would prevent the increase in electrical resistance while maintaining the amorphous structure. Coatings with different film thicknesses were prepared by using the solution plasma method. The thinnest sample was oven sintered to optimize the structure, especially the surface and interface of the layer. The battery capacity from charge-discharge experiments and the resistance change of each part from electrochemical impedance measurements were evaluated. The results showed that the coating layer increased the electrical resistance of the graphite anode. On the other hand, the resistance of the SEI layer was reduced by the coating layer. It can be predicted that the addition of the coating layer will increase the total charge transfer resistance (Rct) of the cell but will also improve the period average capacity in the long run. To be used as a practical material, the film thickness would need to be further reduced, and the balance between the loss of charge transfer resistance and the gain of SEI layer resistance would need to be further optimized.

DOI： 10.1021/acsomega.3c10502

First-principles studies of enhanced oxygen reduction reactions on graphene- and nitrogen-doped graphene-coated platinum surfaces Open Access

Nam H.N., Phung Q.M., Choeichom P., Yamauchi Y., Saito N.

Physical Chemistry Chemical Physics Vol. 26 ( 14 ) page： 10711 - 10722 2024.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Physical Chemistry Chemical Physics

Developing innovative platinum-based electrocatalysts and enhancing their efficiency are crucial for advancing high-performance fuel cell technology. In this study, we employed DFT calculations to provide a theoretical basis for interpreting the impact of graphene coatings on various Pt surfaces on oxygen reduction reaction (ORR) catalytic activity, which are currently applied as protective layers in experiments. We comprehensively assess the geometric and electronic properties of Pt(100), Pt(110), and Pt(111) surfaces in comparison to their graphene-coated counterparts, revealing different adsorption behaviors of O2 across these surfaces. The ORR mechanisms on different Pt surfaces show distinct rate-determining steps, with Pt(111) showing the highest ORR activity, followed by Pt(110) and Pt(100). Graphene coatings play a key role in enhancing charge transfer from the surface, resulting in modifications of O2 adsorption. Despite influencing ORR kinetics, these graphene-coated surfaces demonstrate competitive catalytic activity compared to their bare counterparts. Notably, Pt(111) with a graphene coating exhibits the lowest activation energy among graphene-coated surfaces. Our calculations also suggest that the ORR can occur directly on non-defective Pt@graphene surfaces rather than being restricted to exposed Pt centers due to point defects on graphene. Furthermore, our work highlights the potential of nitrogen doping onto the Pt(111)@C surface to further enhance ORR activity. This finding positions nitrogen-doped Pt@C as a promising electrocatalyst for advancing electrochemical technologies.

DOI： 10.1039/d4cp00269e

Nanoarchitectonics Solution Plasma Polymerization of Amino-Rich Carbon Nanosorbents for Use in Enhanced Fluoride Removal International coauthorship

Tipplook M., Tanaka H., Sudare T., Hagio T., Saito N., Teshima K.

ACS Applied Materials and Interfaces Vol. 16 ( 6 ) page： 7038 - 7046 2024.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ACS Applied Materials and Interfaces

Amino-functionalized carbon (NH2C) is an effective adsorbent in removing pollutants from contaminated water because of its high specific surface area and electrical charge. In the conventional preparation method, the introduction of amino groups onto the carbon surface is limited, resulting in low pollutant adsorption. Herein, we present simultaneous carbonization and amination to form NH2C via electrical discharge of nonequilibrium plasma, and the resultant material is applied as an effective adsorbent in fluoride removal. The simultaneous process introduces numerous amino groups into the carbon framework, enhancing the adsorption efficiency. The fluoride adsorption capacity is approximately 121.12 mg g-1, which is several times higher than those reported in previous studies. Furthermore, computational modeling is performed to yield deeper mechanistic insights into the molecular-level adsorption behavior. These data are useful in designing and synthesizing advanced materials for applications in water remediation.

DOI： 10.1021/acsami.3c15172

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